Laser material processing systems or laser engraving machines are capable of directing a laser in a controlled pattern in order to etch and cut materials such as acrylic, or burn and mark materials such as wood or metal. They include a laser source, beam steering apparatus, beam focusing apparatus, a controller capable of directing the position of the laser output, and a surface or workspace into which objects can be placed for the laser engraving machine to act upon them.
The output from the laser produces heat energy at the point of focus. Depending on the power of the laser and the material being engraved, the laser's energy may vaporize portions of the material or cut completely through it. With other materials or at lower power settings, the top layer of the material may be burned or charred to produce patterns, images, or words. Common materials used in engraving are plastics, wood, leather, and some types of metal.
Laser material processing systems can be controlled by home or office computer systems in a similar method to traditional ink- and toner-based printers. Using various software and device drivers, laser material processing systems can be instructed to “print” patterns using a laser, including patterns such as images, text, or shapes. The controller positions the laser head at the appropriate x-axis and y-axis positions; some controllers are also able to control the distance between the laser and the material being engraved and thus adjust the z-axis (the engraving plane) as well. Thus, laser engraving machines can be used to cut shapes from a solid sheet of acrylic, to shape blocks of wood into jewelry, or to “print” by burning patterns onto wood or leather signs, belt buckles, or wallets.
Laser engraving machines can vary from very large, industrial machines with a large workspace (the size of which limits the size of the object that can be engraved), to home models of more limited dimensions and workspace capacities. These laser engraving machines are alternately known as laser cutters, and smaller units designed for homes or garages are commonly referred to as “hobby lasers.”
Traditionally, the design of laser engraving machines includes a workspace that is enclosed to some degree. Within the workspace the output of the laser is controlled to move on x, y, and z axes. This design paradigm necessitates the size of the workspace—and hence the size of the object to be engraved—be limited by the overall size of the laser engraving machine itself. In order for the laser engraving machine to operate on an object to be engraved, that object would need to physically fit (in length, width, and height) within the confines of laser engraver. For example, a hobby laser engraving device might only be able to fit objects no more than 24 inches in length, 12 inches in width, and 6 inches deep; objects larger than these dimensions in any direction could not be engraved by a machine of such size. In the field of affordable, relatively compact, easy to ship “hobby lasers” for home use, such limitations meant that these systems could only be used for smaller projects and to engrave smaller objects.
It is standard practice within the industry to provide a method for varying the distance from the engraving plane to the focus optic in combination with a final turning mirror in order to allow a laser material processing system to process varying workpiece thicknesses. The methods used currently in the industry are either: (a) a focusing optic fixed in the vertical up-down direction (z-axis or z space) with an adjustable lower surface that moves the entire material vertically up or down in the z direction, or (b) a limited motion focusing optic in which the motion is constrained such that no part of the vertically moving mechanism can pass above the laser beam path.
The fixed focusing optic method that utilizes a lower surface that travels or moves vertically up and down (a “z table”) is deficient due to the limited range of workpiece thicknesses that can be accommodated within the engraving chamber and remain in focus. The nature of a fixed optic and movable z table requires that the z table be actuated in some manner, leading to restrictions in the range of motion of the z table for a given work area envelope and laser material processing system size. This method requires raising the z table through motorized or manual turning of lead screws or belts. This creates problems due to the additional cost and complexity of the extra motorized or manual z table along with the cost and complexity to ensure the z table is perfectly flat, requiring the need for constant adjustments after transportation. Furthermore, the additional mechanical components required for actuating the entire z table often reduces the area that can be reached by the laser beam in the horizontal left-right direction (x-axis) and/or horizontal forward-backward direction (y-axis).
A limited motion focusing optic eliminates the disadvantages of the travelling z table design but suffers from limited focusing distance because no part of the vertically moving mechanism can pass above the laser beam path. One method for making the focusing optic movable involves a telescoping lens tube in which the lens is mounted to a tube of length A, and this tube slides inside another tube of length B. The problem with this design is that the stroke is limited to length A in cases where A is less than or equal to B; or the stroke is limited to length B in cases where B is less than or equal to A. For a given work cube depth z, the maximum material thickness is limited to the difference in distance between work cube depth z and the maximum stroke length. This design is also limited to a minimum material thickness if the bottom work surface is fixed.
Another method for creating a limited motion optic utilizes a sliding mirror that is still limited because, like with a telescopic lens tube, these methods place the vertical moving/focus mechanism in-line with the final beam-steering mirror leading to limitations in vertical motion such that no part of the sliding mechanism can pass above the laser beam path.
Due to the widespread application and the growth of low-power laser material processing systems for use by small businesses, individual hobbyists, and other non-industrial users, there is a need and demand for a transportable, versatile, and affordable laser engraving system that is able to perform the same functions and engrave materials of the same sizes as larger, more expensive systems. Many laser engraving machines are comprised of cumbersome, monolithic housings, yet still provide only limited functionality and versatility. For instance, some laser processing systems are made of heavy sheet metal that is manipulated into a solid volume shape such as a box or cube; the larger the box, the larger the size of the material that can be engraved. These laser engraving systems are not only difficult and expensive to ship and transport due to their weight and large footprints, but manufacturing and assembly costs are high for such solid volumes. Also, without major modification to the main laser engraving system, such systems are not easily versatile or modular, so as to allow a part to easily be interchanged and/or an attachment to easily be added to allow customized performance of the laser material processing system for particular use applications, including use on certain types of materials, and/or specific shaped materials such as a cylindrical bottle.
Accordingly, there is a need in the art for a modular, versatile, interchangeable, and easily transportable laser processing system that: (a) includes a focusing mechanism that can effectively vary the distance from the engraving plane to the focus optic to allow the processing of varying workpiece thicknesses; (b) allows the processing of materials and workpieces that exceed the dimensions of the processing system's engraving chamber and work area (including in the z-axis); and (c) allows the user to add a variety of specialized modular attachments to perform specialized functions or to process specific types and/or shapes of materials and allows the user to easily interchange parts of the invention for increased functionality and capabilities. A laser processing system that addresses the above-mentioned drawbacks in the art would not only provide a consumer with a wide array of options for materials and workpieces to be processed, but it would be more cost-efficient since (i) a separate laser processing system apparatus would not have to be purchased to cut and engrave specific types or shapes of materials and materials that exceed workspace dimensions, and (ii) the costs for two-dimensional manufacturing and assembly of parts using flat panels would cost less than the three-dimensional manufacturing and assembly of parts for solid, monolithic volume structures of other laser processing systems. Other advantages of the present invention will be apparent to one of ordinary skill in the art in light of the ensuing description of the present invention.